Generally, a human tooth includes three main parts: enamel, dentin, and pulp. The composition of the enamel is almost entirely inorganic mineral, while the dentin is a mixture of inorganic mineral and collagen fiber. The enamel and the dentin make up the hard outer structure of the tooth, and therefore, neither the enamel nor the dentin contain nerve endings. On the other hand, the composition of the pulp portion of the tooth includes flesh tissue that is connected to the circulatory and nerve systems of the human body.
As with other tissues in the body, the pulp of the tooth is subject to infections. When the pulp of a tooth becomes infected the pulp swells. The swelling of the pulp causes pain because the pulp is restricted within the fixed orifice of the hard outer surface of the tooth. This pain is commonly called a toothache, and the infection may eventually result in a necrotic tooth.
One conventional method of dealing with a necrotic tooth is administering a root canal treatment. Generally speaking, during a root canal treatment, a dental professional may use a high-speed drill to penetrate the enamel and dentin and expose the pulp chamber within the tooth. The dental professional may then use an endodontic file to sever the pulp at the apex (apical foramen). To reduce the bacterial load within the pulp chamber, the dental professional may use one or more endodontic files to remove as much of the necrotic pulp as possible from the pulp chamber and root canal.
Once the majority of the necrotic pulp is removed, the dental professional may then disinfect any residual infected tissue that remains in the pulp chamber and/or root canal by hydraulically flushing the pulp chamber and root canal with an antimicrobial solution. The canal is then filled with a temporary anti-microbial compound, such as a calcium hydroxide paste or another antimicrobial/antibiotic, after which the pulp chamber is temporarily sealed. The patient is usually prescribed an oral antibiotic and sent home for a couple of weeks to allow complete treatment of the infection.
When the patient returns to the dental professional's office, the dental professional examines the jaw of the patient apically for any signs of any remaining infection. If there are no signs of infection, the dental professional may proceed to remove the temporary sealing material in order to clean and flush out the root canal. At this point of the root canal procedure, the tooth is prepared for the final sealing process of the root ends. Sealing the root ends isolates the pulp chamber from the connective tissue in the jaw, and also seals in any residual contamination or infectious microbes.
The conventional method of filling and sealing the root ends is accomplished using gutta-percha rubber material. Gutta-percha rubber has physical and chemical properties, including inertness, biocompatibility, melting point, ductility and malleability, which have made the gutta-percha rubber a popular choice to fill root canals. In order to fill and seal the root ends, for example, a dental professional may heat the gutta-percha rubber until it melts. The dental profession then can express or inject the gutta-percha into the root end, essentially filling the root canal from the root end upwards towards the pulp chamber (obturation).
One benefit of using gutta-percha rubbers is that gutta-percha rubber is re-treatable in case the tooth requires further work. In particular, if additional work on the tooth is required at some future time, a dental professional can easily remove the gutta-percha rubber because the gutta-percha rubber is naturally a rubber type material at the temperatures inside a human mouth.
Although gutta-percha rubber has several benefits as a material to fill and seal root canals, gutta-percha rubber also has several disadvantages. For example, the quality of the seal provided by gutta-percha rubber at the root end is highly dependent on how fast the molten gutta-percha rubber is delivered into the root canal prior to cooling. If the delivery process is too slow, the gutta-percha rubber begins to thicken before filling all the tiny spaces and holes within the root canal, which may leave unsealed gaps causing the seal to fail.
In an effort to minimize the disadvantages of gutta-percha rubber, root end sealers have been introduced to the dental industry. Conventional root end sealers deliver a superior seal over conventional gutta-percha because root end sealers are designed to flow into the tiny spaces and irregular gaps that are often difficult to fill with gutta-percha rubber. Moreover, conventional root end sealers are chemically cured (as opposed to gutta-percha rubber that simply hardens upon cooling), which allows the root end sealer time to penetrate all the tiny spaces at the root end and within the root canal before the root end sealer material begins to cure.
Although conventional root end sealers may provide a better seal compared to gutta-percha, conventional root end sealers also have several disadvantages. For example, one disadvantage with conventional root end sealers is the need for the dental professional to continue to use gutta-percha as an additional step after the root end sealer placement. In particular, conventional root end sealers typically cure into a hardened composite, which is much more difficult to remove than gutta-percha. Therefore, because dental professionals prefer the root end to be re-treatable after a root canal, dental professionals add a gutta-percha cone around the root-end sealer to allow future access to the root canal.
Additionally, conventional root end sealers have the disadvantage of requiring the dental professional to mix two compositions together just prior to delivery into the root canal. For example, conventional root end sealers may require the dental professional to mix two pastes together. This process takes valuable time, which of course makes the root canal procedure more expensive. Moreover, if the dental professional doesn't mix the two pastes properly, then the root sealer will not cure properly and the seal will likely fail.
Another disadvantage of conventional root end sealers is that the composition of conventional root end sealers may be limited to the chemical compatibility with various active ingredients that would be beneficial to include in the root end sealer. For example, conventional root end sealers may not be chemically compatible with active ingredients, such as calcium hydroxide, which is a popular anti-microbial agent used in dentistry. The main reason for the incompatibility is because calcium hydroxide is renowned for the deactivation of chemical cured cements used in conventional root end sealers.
Accordingly, there are a number of disadvantages in the conventional art of obturation materials.